Re: kern/40408 (panic: PG_ZERO page isn't zero-filled)

[Mindaugas Rasiukevicius <rmind%netbsd.org@localhost>]

> >Number:         40409
> >Category:       kern
> >Synopsis:       panic: PG_ZERO page isn't zero-filled
>
> ...
> 
> db{2}> bt
> breakpoint() at netbsd:breakpoint+0x5
> cpu_Debugger() at netbsd:cpu_Debugger+0x9
> panic() at netbsd:panic+0x260
> uvm_pagezerocheck() at netbsd:uvm_pagezerocheck+0x80
> uvm_pagefree() at netbsd:uvm_pagefree+0x38c
> pmap_update() at netbsd:pmap_update+0x75
> pmap_destroy() at netbsd:pmap_destroy+0x16f
> uvmspace_free() at netbsd:uvmspace_free+0xcc
> uvm_proc_exit() at netbsd:uvm_proc_exit+0x9e
> exit1() at netbsd:exit1+0x1c3
> sys_exit() at netbsd:sys_exit+0x53
> syscall() at netbsd:syscall+0xb6

http://nxr.netbsd.org/source/xref/sys/arch/x86/x86/pmap.c#4704

- Since swap of l->l_md.md_gc_ptp; value is not atomic, is it safe?
- Could comment be added why (where?) pages are expected to be zero-filled,
  that is, why setting PG_ZERO?

-- 
Best regards,
Mindaugas